Hydrostatic transmission

ABSTRACT

A hydrostatic transmission including a variable capacity pump controlled by an adjustable swash plate and a variable motor driven by the pump and controlled by an adjustable swash plate. Mechanical motion transmitting means connects the pump and motor swash plates for causing movement of one of the swash plates at a predetermined variable rate so that a single hydraulic piston and cylinder unit can adjust both swash plates simultaneously.

[ Sept. 11, 1973 Hann et al.

[ HYDROSTATIC TRANSMHSSION 8/1964 Thoma et al.... 3,247,919 4/1966lnventors: Allan C. Rusch, Livonia; John Bubak, Warren, both of Mich.

[73] Assignee: Massey-Ferguson, Enc., Detroit, rimary Examiner-Edgar W.Geoghegan Mich. AttorneyJohn L. Shortley et al.

[57] ABSTRACT A hydrostatic transmission including a variable capac-[22] Filed: Nov. 1, 1971 Appl. No.: 194,106

ity pump controlled by an adjustable swash plate and a variable motordriven by the pump and controlled by an adjustable swash plate.Mechanical motion transmit- [52] U.S. Cl. 60/492 [51} Fl6h 39/46 60/52VS, 53 A, 490,

lint.

ting means connects the pump and motor swash plates for causing movementof one of the swash plates at a predetermined variable rate so that asingle hydraulic h C r a e piston and cylinder unit can adjust bothswash plates simultaneously.

[ 56] References Cited UNITED STATES PATENTS 3,052,098 9/1962 60/53 A 7Claims, 2 Drawing Figures PATENTEU SEPI I I973 SHEU 2 BF 2 My m Mm$55232? BY 1.75/12! BaJa/i (a ATTo RNEYs 1 aYpsos'rA'rrc TRANSMISSIONThis invention relates generally to hydrostatic transmissions, and isparticularly concerned with hydrostatic transmissions of the typeincluding a variable capacity pump controlled by a variable angleWobbler or swash plate control member as well as a variable capacitymotor controlled by a variable angle Wobbler or swash plate controlmember.

In hydrostatic transmissions having both a variable capacity pump and avariable capacity motor, the displacement of both the pump and the motoris controlled by varying the position of a Wobbler or swash platecontrol member. Generally, two piston and cylinder assemlies arerequired for such transmissions, one for adjusting the position of themotor wobbler or swash plate, and one for adjusting the position of thepump wobbler or swash plate. Moreover, different speed and loadrequirements can be met only by adjusting the swash plate at differentrates. Agricultural tractors and similar vehicles require transmissionsthat can provide a wide variety of output torques to meet the varyingoperating conditions of the vehicle. In order to change from oneoperating condition to another, the swash plates frequently must beadjusted at variable rates, that is the angle of adjustment of the pumpswash plate may frequently be different from the angle of adjustment ofthe motor swash plate for efficient performance.

Prior art transmissions of this type generally include a separatehydraulic power system for adjusting the pump and motor swash plates anda complex linkage system interconnecting the two hydraulic power systemswith a control handle. The hydraulic power systems generally include apiston and cylinder assembly for each swash plate, and a control valveand follow-up mechanism for eachof the piston and cylinder assemblies.See, for example, US. Pat. Nos. 3,508,401 and 3,522,704.

An object of this invention is to provide mechanical motion transmittingmeans connecting the pump and motor swash plates for causing one of theswash plates to move in response to movement of the other of the swashplates at a predetermined variable rate so that a single hydraulic powerelement can position both swash plates.

A further object is to provide a hydrostatic transmission having avariable capacity pump and a variable capacity motor with motiontransmitting means connecting the pump and motor swash plates that canbe operated by a single power element to cause the pump and motor swashplatesto assume the proper position to provide optimum performance forvarying conditions of operation.

ln carrying out the foregoing, and other objects, a hydrostatictransmission according to the present invention includes a variableangle pump swash plate control member and a variable angle motor swashplate control member. Motion transmitting means interconnects the pumpand motor control members causing movement of one of the control membersin response to movement of the other of the control members at apredetermined variable rate so that in any position of one of the 7control members, the other control member is in a predetermined positionwith respect thereto to provide a predetermined output torque oroperating efficiency for the transmission. The motion transmitting meansincludes a cam lever which is movable in response to movement of thepump swash plate or control member to cause movement of the motorcontrol member at a rate which is determined by the relative angularpositions of the pump and motor control members. The cam lever isconnected through a link with the pump control member so that cam leverrotates about its fulcrum in response to movement of the pump controlmember. The motor control member has a follower which engages the camsurface on the cam lever so that rotation of the cam lever in responseto angular adjustment of the pump control-member causes angularadjustment of the motor control member in accordance with the contour ofthe cam surface. A power element in the form of a piston and cylinderassembly is connected with one of the control members to provide a poweradjustment of the control members during operation.

Other objects, advantages and features of the invention will becomeapparent from the following description taken in connection with theaccompanying drawings in which:

FIG. 1 is a plan view, partially in section, of a hydrosion 4 alsoincludes a variable capacity motor 10 hydraulically connected to bedriven by the pump 6, and having a variable angle swash plate controlmember 12 for controlling the displacement of the motor 10.

Pump 6 is driven by an input shaft 14 connected with the engine or powerplant of-the vehicle. The input shaft 14 extends through thetransmission and is connected by a coupler 16 to a power take-off shaft18 so that the power take-off shaft is constantly driven by the inputshaft at a speed proportional to the speed of the engine. The motor 10has an output shaft 20 which is connected through a planetary gearassembly, indicated genrally by reference numeral 22, with a drie shaft24.

The planetary gear assembly 22 includes a ring gear 26 which is splinedto the motor shaft 20, a sun gear 28 which is splined to the input shaft14, and a planet gear 32 carried by a planet carrier 30 which in turn issplined to the drive shaft 24. The planet gear 32 is meshed with thering gear Mind the sun gear 28. Therefore, the speed and direction ofrotation of the planet carrier 30, and hence the drive shaft 24, isdetermined by the relative speed and direction of the motor shaft 20 andsun gear 28. If the motor shaft 20 is stationary, the ring gear 26 willbe stationary and the planet carrier 30 will be driven solely by the sungear 28. Therefore, the speed and direction of the drive shaft 24 isvaried in accordance with variations in the speed and direction of themotor shaft 20. The speed and direction of the motor shaft 20 isdetermined by the positions of the swash plate control members 8 and 12.

In order to obtain the desired speed, output torque and output power forthe drive shaft 24 under various operating conditions, the relativeangular positions of the pump control member 8 and motor control member12 must vary to meet the predetermined performance requirements of thetransmission. For example, there may be a range of output speed, torqueand power requirements that can best be obtained by changing the angleof the pump control member 8 with little or no corresponding change inthe angle of the motor control member 12. There may be still anotherrange of output speed, torque and power requirements that can best beobtained by adjusting the angle of both the pump control member 8 andthe motor control member 12 to obtain the different speed, torque andpower values throughout the range. Thus, in one range,

the change is brought about solely by changing the angle of the pumpcontrol member 8, and in the other range, a change is brought about byadjusting both the pump and motor control members 8 and 12,respectively, but by different amounts. In accordance with the presentinvention, motion transmitting means indicated collectively by referencenumeral 34 interconnects the pump and motor control members 8 and 12causing movement or adjustment of one of the control members in responseto movement of the other control member at a predetermined variablerate.

The motion transmitting means 34 includes a cam lever 36 fulcrummed on afixed support in the form of a rod 38 mounted on supporting portions ofthe housing 2. The cam lever is movable about the axis of the rod 38 inresponse to movement of the control members 8 and 12 to cause movementof one of the control members relative to the other control member at arate that varies in accordance with the relative angular positions ofthe control members 8 and 12.

The pump control member 8 has a pair of spaced arms 46 and 42 (FIG. 2).A link 44 connects the pump control member 8 with the cam member 36 tocause rotation of the cam lever 36 in response to movement of the pumpcontrol member 8. The link 44 has a bifurcated or forked end portion 46which receives arm 42 of the control member 8 and is pivotally connectedthereto by a pin 48. The cam lever 36 is formed with a lug 52 (FIG. 2)defining a slot 54'which receives the other end of link 44, and a pin 50pivotally connects link 44 with the cam lever 36.

The motor control member 12 is formed with an arm 58 on which is mounteda cam follower roller 60. Roller 60 is engaged in a cam groove 62 formedin the cam lever 36. Movement of the pump control member 8 angularlycauses link 44 to rotate the cam lever 36 about its fulcrum 38. Rotationof lever 36 in turn acts through the cam follower 60 to cause angularadjustment of the motor control member 12 at a rate determined by theposition of the cam follower 60 in the cam groove 62. The cam groove 62is roughly of U-shape having a base portion 62a and leg portions 62b.The configuration ofthe cam groove 62 determines the angularrelationship between the pump control member 8 and the motorcontrolmember l2 and hence the relationship between the pumpdisplacement and the motor displacement.

Power element 64 includes a piston slidably mounted in a cylinder 68.The piston has a rod 66 which reciprocates with respect to cylinder 68in response to the delivery of hydraulic oil to and from the cylinder.Cylin der 68 is pivotally mounted on the rod 38, and the piston rod 66is pivotally connected by a pin 82 with arm 40 of the pmp control member8.

A return-to-neutral spring assembly designated collectively by referencenumeral 79 is mounted on the piston rod 66. The spring assembly '76includes a pair of flanged spring seat members 72 and 74 slidablymounted on piston rod 66, a pair of snap rings 76 and 78 mounted on rod66 in spaced locations along the length of rod 66, and a spring 60seated between the spring seat members 72 and 74 and biasing the springseat members 72 and 74 toward engagement with the snap rings 76 and 78respectively. The power element 64 is connected in a conventional closedloop servo system (not shown) under the control of the vehicle operatorso that the control members 8 and i2 can be adjusted as desired by theoperator. As the piston rod 66 is retracted into cylinder 68, or towardthe left in FIG. I, the spring seat member 72 engages the end wall ofcylinder 68, and spring 80 is compressed upon further movement of rod 66toward the left with respect to the cylinder. In the event of asubsequent loss of pressure, spring 80 will expand to return controlmember 8 to a neutral position.

While a specific form of the invention has been illustrated anddescribed in the foregoing specification and accompanying drawings, itwhould be understood that the invention is not limited to the exactconstruction shown but that various alternatives in the construction andarrangement of parts, all falling within the scope and spirit of theinvention will be apparent to thos skilled in the art.

We claim:

1. Hydrostatic transmission apparatus comprising: a fixed support; apump; an adjustable pump control member for controlling the displacementof the pump; a motor hydraulically connected to be driven by said pump,and an adjustable motor control member for controlling the displacementof the motor, actuating means characterized in that a cam lever and alink are connected between said pump and motor control members forcausing movement of one of said control members in response to movementof the other of said con trol members and the combined lever and linkare in side-by-side relation with the actuating means and that said camlever and actuating means are pivotally connected to such fixturesupport.

2. Apparatus as claimed in claim 1 characterized in that a cam surfaceis defined on said cam lever and a follower on said other control memberis slidably engaged with said cam surface.

3. Apparatus as claimed in claim 2 characterized in that said camsurface comprises a groove in said cam lever and said follower isengaged in said groove.

4. Hydrostatic transmission apparatus as set forth in claim 1 whereinsaid cam lever and said actuating means are mounted to pivot about thesame axis.

5. Hydrostatic transmission apparatus as set forth in claim 1 whereinsaid fixed support is a fixed shaft extending transverse to said pumpand motor and at one end thereof.

6. Hydrostatic transmission apparatus as set forth in claim 9 which saidshaft is at the motor end.

7. Hydrostatic transmission apparatus as set forth in claim 1 whereinsaid actuating means is connected to one control member and said camlever is connected to the other control member.

' :u a m t t

1. Hydrostatic transmission apparatus comprising: a fixed support; apump; an adjustable pump control member for controlling the displacementof the pump; a motor hydraulically connected to be driven by said pump,and an adjustable motor control member for controlling the displacementof the motor, actuating means characterized in that a cam lever and alink are connected between said pump and motor control members forcausing movement of one of said control members in response to movementof the other of said control members and the combined lever and link arein side-by-side relation with the actuating means and that said camlever and actuating means are pivotally connected to such fixturesupport.
 2. Apparatus as claimed in claim 1 characterized in that a camsurface is defined on said cam lever and a follower on said othercontrol member is slidably engaged with said cam surface.
 3. Apparatusas claimed in claim 2 characterized in that said cam surface comprises agroove in said cam lever and said follower is engaged in said groove. 4.Hydrostatic transmission apparatus as set forth in claim 1 wherein saidcam lever and said actuating means are mounted to pivot about the sameaxis.
 5. Hydrostatic transmission apparatus as set forth in claim 1wherein said fixed support is a fixed shaft extending transverse to saidpump and motor and at one end thereof.
 6. Hydrostatic transmissionapparatus as set forth in claim 9 which said shaft is at the motor end.7. Hydrostatic transmission apparatus as set forth in claim 1 whereinsaid actuating means is connected to one control member and said camlever is connected to the other control member.